From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757982Ab2GFQgc (ORCPT ); Fri, 6 Jul 2012 12:36:32 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:43280 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757906Ab2GFQga (ORCPT ); Fri, 6 Jul 2012 12:36:30 -0400 Date: Fri, 6 Jul 2012 09:33:38 -0700 From: "Paul E. McKenney" To: Frederic Weisbecker Cc: LKML , Alessio Igor Bogani , Andrew Morton , Avi Kivity , Chris Metcalf , Christoph Lameter , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , "H. Peter Anvin" , Ingo Molnar , Josh Triplett , Kevin Hilman , Max Krasnyansky , Peter Zijlstra , Stephen Hemminger , Steven Rostedt , Sven-Thorsten Dietrich , Thomas Gleixner Subject: Re: [PATCH 6/6] x86: Exit RCU extended QS on notify resume Message-ID: <20120706163338.GW2522@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1341576018-10721-1-git-send-email-fweisbec@gmail.com> <1341576018-10721-7-git-send-email-fweisbec@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1341576018-10721-7-git-send-email-fweisbec@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12070616-1780-0000-0000-0000072A241A X-IBM-ISS-SpamDetectors: X-IBM-ISS-DetailInfo: BY=3.00000284; HX=3.00000191; KW=3.00000007; PH=3.00000001; SC=3.00000004; SDB=6.00154304; UDB=6.00034812; UTC=2012-07-06 16:36:28 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 06, 2012 at 02:00:18PM +0200, Frederic Weisbecker wrote: > do_notify_resume() may be called on irq exit but it won't > be protected between rcu_irq_enter() and rcu_irq_exit() > and we don't call rcu_user_exit() on irq entry (unlike > syscalls/exceptions entry). > > Since it can use RCU read side critical section, we must call > rcu_user_exit() before doing anything there. > > This complete support for RCU userspace extended quiescent state > in x86. > > Signed-off-by: Frederic Weisbecker > Cc: Alessio Igor Bogani > Cc: Andrew Morton > Cc: Avi Kivity > Cc: Chris Metcalf > Cc: Christoph Lameter > Cc: Geoff Levand > Cc: Gilad Ben Yossef > Cc: Hakan Akkan > Cc: H. Peter Anvin > Cc: Ingo Molnar > Cc: Josh Triplett > Cc: Kevin Hilman > Cc: Max Krasnyansky > Cc: Peter Zijlstra > Cc: Stephen Hemminger > Cc: Steven Rostedt > Cc: Sven-Thorsten Dietrich > Cc: Thomas Gleixner > --- > arch/x86/Kconfig | 1 + > arch/x86/kernel/signal.c | 2 ++ > 2 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index c70684f..38dfcc2 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -95,6 +95,7 @@ config X86 > select KTIME_SCALAR if X86_32 > select GENERIC_STRNCPY_FROM_USER > select GENERIC_STRNLEN_USER > + select HAVE_RCU_USER_QS if X86_64 And I will bite yet again. Why only 64-bit kernels? Thanx, Paul > config INSTRUCTION_DECODER > def_bool (KPROBES || PERF_EVENTS || UPROBES) > diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c > index 21af737..5af078e 100644 > --- a/arch/x86/kernel/signal.c > +++ b/arch/x86/kernel/signal.c > @@ -776,6 +776,8 @@ static void do_signal(struct pt_regs *regs) > void > do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags) > { > + rcu_user_exit(); > + > #ifdef CONFIG_X86_MCE > /* notify userspace of pending MCEs */ > if (thread_info_flags & _TIF_MCE_NOTIFY) > -- > 1.7.5.4 >